Optical Resonators Based On Surface Plasmon MIM Waveguides

Surface plasmon polaritons (SPPs), also known as surface plasmon, are electromagnetic nonradiative surface modes formed by interaction of free electrons of metallic surface with incident photons. Surface plasmon polaritons, which are evanescent waves propagating along a metal-dielectric interface, show a strong localized enhancement effect at nano-scale. One can realize the transmission and control of the electromagnetic waves at subwavelength scale by using the property of surface plasmon mentioned above. Nano photonic devices based on surface plasmon are the foundation of nano all-optical network, so how to realize the valid control of surface plasmon at nano-scale becomes the research hotspot. There are no radiation mode and leakage mode in those structures based on metal MIM surface plasmon waveguide, so the electromagnetic waves can highly localize on subwavelength structure, thus realizing the transmission in nanometer scale. In recent years, functional devices based on insulator-metal-insulator waveguide structures have been designed, such as optical splitters, directional couplers, Bragg reflectors, filters, and researchers controlled functions of the structure by altering its geometry and the material parameters. In this thesis, we designed several resonators based on MIM waveguide, and studied the transmission characteristics in the visible and near infrared regions.The main research works and conclusions are as following:A novel resonator based on MIM waveguide, which consists of a nanodisk cavity with a rectangular metal strip and two straight MIM waveguides, is proposed. We mainly studied the influence of the transmission characteristic for the size and rotation degree of the metal strip in the visible and near infrared regions. The results show that when the metal strip’s width is about dozens of nanometer, the proposed structure presents band-pass filtering property, and that the filtering wavelengths can be tuned by altering the length of the strip. When we rotate the metal strip, a new resonant mode occurs; the rotation degree not only influences the resonating wavelength, but also control the intensity of the resonance. When the metal strip’s width and length are more than two hundred nanometer, the structure works as a bend waveguide instead of a filter.A composite structure which consists of a square cavity with a rectangular metallic strip and two straight MIM, waveguides, is proposed. We mainly studied the influence of the transmission characteristic for the size of the metal strip, and compared the results with the disk’s mentioned above, which turned out to be very similar. When the metal strip width is about dozens of nanometer, the proposed structure presents band-pass filtering property, and filtering wavelength can be tuned by altering the length of the strip. When the metal strip is rotated, there are two transmission peaks on the transmission spectrum, which corresponding to two resonant modes; we can fine tune the resonating wavelength by altering the rotation degree, and also can control the intensity of resonance. When the metal strip’s width and length are more than two hundred nanometer, the structure works as a waveguide instead of a filter.A defective rectangular ring resonator based on MIM waveguide is investigated. We mainly focus on the effects of the size and location of the defect on the transmission properties of the structure. The transmission spectra and magnetic field distribution at resonance wavelengths are numerically simulated, which are compared with the calculation result of transmission line model to confirm the transmission property. Compared to perfect rectangular ring resonator, structure with defect destroys the symmetry of the resonant modes in the resonator, resulting in novel filtering function of the complex resonator. The effective length of the structure depends on the size of the defect, so filtering wavelength can be tuned by adjusting the dimension of the defect. In addition, the coupling strength between the waveguide and defective rectangular ring resonator is dependent on the defect location, which is useful to control the transmittance at filtering wavelength; When the size of detect is chosen on a certain value, a new double degenerated mode appears, which improves the filtering properties of the structure. The structure can realize more broadband segment filtering, effectively adjust filtering wavelength, and control transmittance without changing the overall size.